On 23 November 1963, the Fourth Doctor and K9 Mark II return to Totter's Lane to retrieve a Heshrax insect which he had been tracking the day that he left. While there, they meet Debbie, Susan's best friend from Coal Hill School. Debbie, who turned fifteen that day, was concerned about Susan's sudden disappearance as she knew that Susan would never miss her birthday. She had met the First Doctor on one occasion but the Fourth Doctor did not recall seeing her before. He also did not remember Susan ever mentioning Debbie but admitted that he was not always the best listener.